/*
 * ASN.1 DER parsing
 * Copyright (c) 2006, Jouni Malinen <j@w1.fi>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * Alternatively, this software may be distributed under the terms of BSD
 * license.
 *
 * See README and COPYING for more details.
 */

// #include "includes.h"
#include <stdio.h>
#include "stdint.h"
#include "asn1.h"
#include "jumbo.h"

#define printf(...)

int asn1_get_next(const uint8_t *buf, size_t len, struct asn1_hdr *hdr)
{
    const uint8_t *pos, *end;
    uint8_t tmp;

    memset(hdr, 0, sizeof(*hdr));
    pos = buf;
    end = buf + len;

    hdr->identifier = *pos++;
    hdr->class = hdr->identifier >> 6;
    hdr->constructed = !!(hdr->identifier & (1 << 5));

    if ((hdr->identifier & 0x1f) == 0x1f) {
        hdr->tag = 0;
        do {
            if (pos >= end) {
                printf("ASN.1: Identifier "
                        "underflow");
                return -1;
            }
            tmp = *pos++;
            printf("ASN.1: Extended tag data: "
                    "0x%02x", tmp);
            hdr->tag = (hdr->tag << 7) | (tmp & 0x7f);
        } while (tmp & 0x80);
    } else
        hdr->tag = hdr->identifier & 0x1f;

    tmp = *pos++;
    if (tmp & 0x80) {
        if (tmp == 0xff) {
            printf("ASN.1: Reserved length "
                    "value 0xff used");
            return -1;
        }
        tmp &= 0x7f; /* number of subsequent octets */
        hdr->length = 0;
        if (tmp > 4) {
            printf("ASN.1: Too long length field");
            return -1;
        }
        while (tmp--) {
            if (pos >= end) {
                printf("ASN.1: Length "
                        "underflow");
                return -1;
            }
            hdr->length = (hdr->length << 8) | *pos++;
        }
    } else {
        /* Short form - length 0..127 in one octet */
        hdr->length = tmp;
    }

    if (end < pos || hdr->length > (unsigned int) (end - pos)) {
        printf("ASN.1: Contents underflow");
        return -1;
    }

    hdr->payload = pos;
    return 0;
}


int asn1_parse_oid(const uint8_t *buf, size_t len, struct asn1_oid *oid)
{
    const uint8_t *pos, *end;
    unsigned long val;
    uint8_t tmp;

    memset(oid, 0, sizeof(*oid));

    pos = buf;
    end = buf + len;

    while (pos < end) {
        val = 0;

        do {
            if (pos >= end)
                return -1;
            tmp = *pos++;
            val = (val << 7) | (tmp & 0x7f);
        } while (tmp & 0x80);

        if (oid->len >= ASN1_MAX_OID_LEN) {
            printf("ASN.1: Too long OID value");
            return -1;
        }
        if (oid->len == 0) {
            /*
             * The first octet encodes the first two object
             * identifier components in (X*40) + Y formula.
             * X = 0..2.
             */
            oid->oid[0] = val / 40;
            if (oid->oid[0] > 2)
                oid->oid[0] = 2;
            oid->oid[1] = val - oid->oid[0] * 40;
            oid->len = 2;
        } else
            oid->oid[oid->len++] = val;
    }

    return 0;
}


int asn1_get_oid(const uint8_t *buf, size_t len, struct asn1_oid *oid,
        const uint8_t **next)
{
    struct asn1_hdr hdr;

    if (asn1_get_next(buf, len, &hdr) < 0 || hdr.length == 0)
        return -1;

    if (hdr.class != ASN1_CLASS_UNIVERSAL || hdr.tag != ASN1_TAG_OID) {
        printf("ASN.1: Expected OID - found class %d "
                "tag 0x%x", hdr.class, hdr.tag);
        return -1;
    }

    *next = hdr.payload + hdr.length;

    return asn1_parse_oid(hdr.payload, hdr.length, oid);
}


void asn1_oid_to_str(struct asn1_oid *oid, char *buf, size_t len)
{
    char *pos = buf;
    size_t i;
    int ret;

    if (len == 0)
        return;

    buf[0] = '\0';

    for (i = 0; i < oid->len; i++) {
        ret = snprintf(pos, buf + len - pos,
                "%s%lu",
                i == 0 ? "" : ".", oid->oid[i]);
        if (ret < 0 || ret >= buf + len - pos)
            break;
        pos += ret;
    }
    buf[len - 1] = '\0';
}


static uint8_t rotate_bits(uint8_t octet)
{
    int i;
    uint8_t res;

    res = 0;
    for (i = 0; i < 8; i++) {
        res <<= 1;
        if (octet & 1)
            res |= 1;
        octet >>= 1;
    }

    return res;
}


unsigned long asn1_bit_string_to_long(const uint8_t *buf, size_t len)
{
    unsigned long val = 0;
    const uint8_t *pos = buf;

    /* BER requires that unused bits are zero, so we can ignore the number
     * of unused bits */
    pos++;

    if (len >= 2)
        val |= rotate_bits(*pos++);
    if (len >= 3)
        val |= ((unsigned long) rotate_bits(*pos++)) << 8;
    if (len >= 4)
        val |= ((unsigned long) rotate_bits(*pos++)) << 16;
    if (len >= 5)
        val |= ((unsigned long) rotate_bits(*pos++)) << 24;
    if (len >= 6)
        printf("X509: %s - some bits ignored "
                "(BIT STRING length %lu)",
                __func__, (unsigned long) len);

    return val;
}
